(i) Field of the Invention
This invention relates to traveling performance of an optical pickup in an access operation and, more particularly, to an optical disc drive capable of preventing tooth jumping and step-out from occurring in a gear feed mechanism of an optical pickup to improve the recording/reproducing performance.
(ii) Described of the Related Art
Stable recording/reproducing in optical disc drives requires improved traveling performance of an optical pickup moving in the radial direction of a disc.
In an optical pickup driving system of a slim-type optical disc drive, a screw gear mounted integrally with a rotation shaft of a stepper motor is meshed with a guide feed gear provided on a housing of the optical pickup. With the rotation of the stepper motor, the driving force is transmitted to the optical pickup, so that the optical pickup travels in the radial direction of a disc.
At this stage, the guide feed gear is pressed against the screw gear by a constant pressing force. If hard acceleration of traveling is applied, the guide feed gear runs on to the screw gear, causing a phenomenon of tooth jumping, step-out or the like between the gears. Accordingly, a proper pressing force of the guide feed gear against the screw gear in accordance with an access condition is required for an improvement in the traveling performance of the optical pickup.
In the related art, there is structure of using a leaf spring, a spring or the like to press a gear provided on a guide feed against a screw gear.
JP-A No. 2003-288763 discloses the structure in which two gears provided on a guide feed is formed of a leaf spring and pressed against a screw gear.
The art described in JP-A No. 2003-288763 is the structure of pressing two protrusions (gears) provided on an optical pickup against a groove of a screw gear in separated positions. However, since a sheet-shaped leaf spring giving a pressing force to the protrusions is fixed in asymmetric positions of the two protrusions, different pressing forces are applied to the screw gear.
On the other hand, since the optical pickup moves (travels) in a range from the inner periphery to the outer periphery of a disc, the screw gear and the gears provided on the optical pickup differ in press characteristics from each other.
The press characteristics of the optical pickup are desirably exhibited equally in the range from the inner periphery to the outer periphery of a disc at all times. For this purpose, symmetric structure is required for the structure of pressing the two gears provided on the optical pickup against the screw gear.